Electron discharge device



Sept. 14, 1937. J. L. H. JONKER iz-r AL ELECTRON DI S CHARGE DEVI CEOriginal Filed June 22, 1931 INVENTOR JOHAN L.H.JONKEPs WIVEggBPHGHT BYMlrf l ATTORNEY Patented Sept. 14, 1937 UNITED STATES ELECTRON DISCHARGEDEVICE Johan Lodewijk Hendrik Jonker, Eindhoven, and

Wilhelm Albricht, The Hague, Netherlands, assignors to Radio Corporationof America, a corporation of Delaware Original application June 22,1931, Serial No. 545,946. Divided and this application June 28, 1933,Serial No. 678,040. In the Netherlands June 21, 1930 5 Claims.

This application is a division of application S. N. 545,946 entitledAmplifying circuit arrangement with parallel supply filed June 22nd 1931and issued as Patent No. 1,957,542.

With this kind of circuit the direct current is commonly supplied to theanode through a choke coil opposing a very high impedance to all thefrequencies to be amplified. In parallel with the direct-current circuitis connected an alternating current circuit which is blocked for directcurrent by means of a condenser.

In order to obtain the greatest possible amplification with acircuit-arrangement of the kind above referred to, the impedance of thechoke coil for all the frequencies to be amplified must practically beinfinitely high. This condition can hardly be fulfilled and it hastherefore been proposed to connect a saturated diode instead of thechoke coil. Beside a comparatively low directcurrent resistance such adiode has a very high alternating current resistance which moreover isindependent of the frequency. On superficial consideration the saturateddiode seems to be therefore a coupling element having very favorableproperties. In practice it appears however that the use of a diode doesnot lead to the desired result and that it is impossible to amplify abroad range of frequencies.

The invention is based on the View that the unsatisfactory working ofthis circuit-arrangement is due to the fact that with the use of asaturated diode the filament is connected to abattery or other source ofcurrent, owing to which the filament obtains a comparatively largecapacity with respect to earth. Since on the other hand the filament ofthe amplifier valve has also an appreciable capacity relatively toearth, the

diode acting as a coupling element is shunted by a rather largecapacity. The coupling element consequently has not a very highalternating current resistance for comparatively high fre quencies.

According to the invention, in order to eliminate this drawback use ismade of a diode with an indirectly heated cathode.

With a diode comprising an indirectly heated cathode the capacity of thelatter relatively to earth can be kept very small and need in generalnot be larger than the capacity between the grid and the cathode of thevalve with which the first valve is coupled.

According to the invention, in order to avoid that the capacity of thecathode due to the close proximity of the heating element with theelectric circuits connected thereto obtains notwithcurrent circuit 6 ofthe repeater tube 1.

standing a considerable value, the heating element may be arranged insuch a manner that the electrostatic capacity between the cathode andthe heating element is very small. For example, the heating coil may bearranged at the exterior around the anode so that the supply of heat tothe cathode takes place across the anode. Besides, according to theinvention, use is preferably made of a. cathode which is very thin. Thisaffords the advantage that the electric field strength perpendicular tothe cathode may obtain a high value and this high Value of the fieldstrength causes again that the alternating current resistance of thewhole diode is altered.

In fact, the alternating current impedance of the saturated diode whichat first seems to be infinitely high, depends in reality on the absolutetemperature and on the electric field strength at the surface of thecathode.

The general character of the expression of the alternating currentresistance is thus:

In this expression a denotes a constant, T the absolute temperature andF the field strength perpendicular to the cathode surface. When use ismade of a heating coil, surrounding the anode,

heating of the latter is of course unavoidable but a heated anode has noharmful effect on the working of the diode, even not if the temperatureis so high that the anode begins to emit, for after being emitted theelectrons immediately attain an electrostatic field which drives themback to the anode.

The invention is disclosed in the accompanying drawing in which Figs. 1and 2 represent diagrammatically an approved form of the apparatus and amodification thereof.

In Fig. 1 the diode 5 is connected in the direct The diode comprises afine wire cathode 8, an anode 9 surrounding the cathode and a heatercoil l0 wound around the exterior of the anode. The anode or B batteryII is connected to the anode 9 of the diode 5. The. directcurrentcircuit for the device I is from the positive side of the batteryH to anode 9, cathode 8, through circuit 6 to the anode of device Ithrough ground to the negative side of battery H.

In the modification illustrated in Fig. 2, the cathode 8 is surroundedby a heater element I2 which comprises the anode of the device.Otherwise the circuit of Fig. 2 is the same as the circuit of Fig. 1.

The invention is applicable to high frequency as well as low frequencyamplifier circuit arrangements of any kind, quite independently of thepurpose for which the apparatus having such a circuit-arrangement isutilized. The invention may also'be applied in order to couple the anodecircuit of a detector valve with the succeeding low frequency amplifieror with a telephone or other indicator.

What we claim is:

1. An electron discharge device comprising a cylindrical anode, acathode extending within the anode, and means disposed externally of theanode and supported thereby for heating said cathode, said heating meansbeing in the form of a bifilar winding adapted to be energized from analternating current source.

2. An electron discharge device comprising a cylindrical anode, acathode extending within the anode, and means supported from the outersurface of the anode for heating said cathode solely by heat radiation,said heating means being in the form of helically-wound parallel wiresadapted to be energized from an alternating current source.

'lindrical tubular anode closed at one end, a cathode extending withinthe anode from the opposite end and coaxially disposed therein, andmeans carried by the outer surface of the anode for heating said cathodesolely by heat radiation.

5. An electron discharge device comprising a cylindrical tubular anodeclosed at one end, a cathode extending within the anode from theopposite end and coaxially disposed therein, and means carried by theouter surface of the anode for heating said cathode solely by heatradiation, said heating means being in the form of a pair of. parallelwires helically-wound and adapted to be energized from an alternatingcurrent source.

JOHAN LODEWIJK HENDRIK JONKER.

WILHELM ALBRICHT.

